• 한국추진공학회지
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• 제24권4호
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• pp.66-72
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• 2020

본 논문은 알루미늄 함량 변화에 따른 추진제의 후경화에 대한 영향성, 화학적 노화도에 관하여 기술하였다. 동일 경화조건에서 알루미늄 함량이 18 wt%인 추진제가 2 wt%인 추진제 대비 후경화 기간이 길어지는 것으로 확인하였다. 반면 후경화가 포함된 화학적 노화도 분석에서는 알루미늄 함량이 18 wt%인 추진제가 2 wt%인 추진제 대비 화학적 노화가 천천히 진행되는 것을 확인하였다.

• 한국연초학회지
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• 제26권1호
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• pp.35-42
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• 2004

This study was carried out to examinate the effect of aging period on chromatic, chemical and organoleptic characteristics, and to evaluate of optimum aging period for each grade in burley leaf tobacco. The leaf tobaccos were produced in 2000, and threshed, redried and packed in carton box under the current methods. Four grades of processed leaf(A3T, B1T, C1W and D3W) were stored during 24 months (May 10, 2001 to April 31, 2003) in warehouse of Chungju Leaf Tobacco Processing Factory. The leaf tobaccos were sampled at three month intervals for analysis of chromatic, chemical and organoleptic properties. pH values of four grades, and Yellow(b) of A3T and BIT were also significantly decreased during the aging. Filling values, tar, nicotine and CO contents of tobacco smoke, and puff number of cigarettes were not significantly changed during the aging. Positive correlation coefficients were significantly observed between irritation of the calculated attributes from contents of volatile oil components in leaf tobacco and that of the panel sensory attributes. The ratio of maximum change in irritation attribute was larger than that in taste attribute during aging. The calculated irritations of 18～24 months aging for A3T and B1T were significantly lower than zero-aging, while those of C1W and D3W were not significant among aging periods. The panel irritations of 12～15 months aging for four grades were low tendency. The results suggest that decrease of aging period for thin leaf from 21～24 to 12～15 months may be beneficial to save storage cost in burley tobacco.

• 한국연초학회지
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• 제26권1호
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• pp.27-34
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• 2004

This study was carried out to examinate the effect of aging period on chromatic, chemical and organoleptic characteristics, and to evaluate of optimum aging period for each grade in flue-cured leaf tobacco. The leaf tobaccos were produced in 2000, and threshed, redried and packed in carton box under the current methods. Four grades of processed leaf(A3O, B1O, C1L and D3L) were stored during 24 months(May 10, 2001 to April 31, 2003) in warehouse of Chungju Leaf Tobacco Processing Factory. The leaf tobaccos were sampled at three month intervals for analysis of chromatic, chemical and organoleptic properties. Yellow(b), pH values and total sugar contents of four grades were significantly decreased during the aging. Filling values, tar, nicotine and CO contents of tobacco smoke, and puff number of cigarettes were not significantly changed during the aging. Positive correlation coefficients were significantly observed between taste and irritation of the calculated attributes from contents of volatile oil components in leaf tobacco and those of the panel sensory attributes. The ratio of maximum change in taste attribute was larger than that in irritation attribute during aging. The optimum aging periods estimated by taste for A3O, B1O, C1L and D3L were 17.8, 14.9, 10.8, and 9.8 months, respectively. The thin leaf(Primings and Cutters) undergo satisfactory aging earlier as compared to bodied leaf(Leaf and Tips). The results suggest that decrease of aging period for thin leaf from 18～21 to 9～12 months may be beneficial to save storage cost in flue-cured tobacco.

• 한국세라믹학회지
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• 제44권1호
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• pp.23-31
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• 2007

To examine the effects of chemical admixture on the fluidity and strength development of high chloride cement, experiments were conducted in which lignosulfonate (LS), naphthalenesulfonate (NS), and polycorboxylate (PC) were each added in standard and excessive amounts, and the results were as follows. 1. Because adding KCl to NS causes a decrease in flow, adding PC is better in maintaining high cement fluidity. 2. When cement contained much chloride comes in contact with water, hydration begins 4 h after contact and securing workability becomes difficult, but by adding PC, workability can be secured to 10 h. 3. The bound water ratio and compressive strength in aging 3 days occupy $70\sim80%$ of those in aging 28 days, and the early compressive strength increases not only by adding KCl, but also by chemical admixture. 4. Although compressive strength development is excellent in NS, PC, if NS is added excessively, hydration becomes slow and while the pore structures become slightly minute, the strength development decreases due to severe setting retardation.

• Applied Biological Chemistry
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• 제35권4호
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• pp.286-293
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• 1992

개량식과 재래식 된장의 기호와 향기의 단점을 개선하고 장점을 유지하기 위하여 재래식, 개량식 그리고 납두를 혼합 제조한 된장의 이화학적 변화와 관능검사에 의한 적정배합 비율과 숙성정도를 검토하였다. pH는 개량식 메주에 납두의 배합량이 높을수록 증가하였으며 재래식 메주의 배합에서는 감소하였다. 재래식 메주에서의 질소화합물 함량은 개량식에서 보다 3배 높았으며 숙성도 빨랐다. 갈색색소의 변화는 초기의 값에 따르며 재래식이 높았다. 개량식과 재래식 그리고 납두를 혼합한 구가 관능적 평가가 높았으며 그 비율은 개량식, 재량식 그리고 남두의 비가 48 : 48 : 5의 비율이었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권3호
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• pp.82-87
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• 2016

This study investigates effects of an aging period on arsenic (As) chemical forms in soils and phytotoxicity using artificially As-contaminated soils with a range of As concentrations (0-300 mg/kg) and aging periods (0 and 3 months). A sequential extraction procedure showed that the increasing As concentration in soils increased the ratio of non-specifically and specifically bound As, which are known to be bioavailable. This resulted in increasing As uptake by tomatoes with increasing As concentration (R²=0.87 for exponential fitting); however, the seed germination was not sensitive to the As concentrations of the soil samples. The seed germination was also statistically similar in the soils with 75 and 150 mg-As/kg regardless of the aging period. The time taken until the seed germination (i.e., lag phase), on the other hand, decreased from 10 d to 3 d with aging for 3 months. This can be attributed to the decreased amount of bioavailable As with aging. Overall, this study shows that when the toxic effects of the As-contaminated soils are assessed using tomato plants, it is better to use more sensitive methods than seed germination such as the As accumulation or the lag phase for seed germination.

• 한국재료학회지
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• 제15권12호
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• pp.773-779
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• 2005

Properties of Ni-base superalloys of Nimonic 80A alloy system were investigated by the observation of microstructures, precipitates ana hardness as a function of the chemical compositions ana the paths of heat treatment. The higher hardness values showed, the higher Ti/Al ratio among high compositions of Cr and Co element. The lower (Ti+Al) and Fe contents decreased in the same Ti/Al ratio, the higher hardness values showed. This results are considered that coherent deformation was increased with increasing Ti/Al ratio. Hardness showed higher value when Cr contents was $18 wt\%$ less than $21wt\%Cr$. In $3.15 wt\%$Co alloy, $\gamma'$ phase was very fine as around 50nm and, its volume fraction and hardness showed the highest value by 2step-aging treatment.

• 한국세라믹학회지
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• 제43권9호
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• pp.564-568
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• 2006

AlO(OH) nano gel is used in precursor of ceramic material, coating material and catalyst. For use of these, not only physiochemical control for particle morphology, pore characteristic and peptization but also studies of synthetic method for preparation of advanced application products were required. In this study, AlO(OH) nano gel was prepared through the aging and drying process of aluminum hydroxides gel precipitated by the hydrolysis reaction of dilute NaOH solution and aluminum sulfate solution. In this process, optimum synthetic condition of AlO(OH) nano gel having excellent pore volume as studying the effect of water and aluminum sulfate mole ratio on gel precipitates has been studied. Water and aluminum sulfate mole ratio brought about numerous changes on crystal morphology, surface area, pore volume and pore size. Physiochemical properties were investigated as using XRD, TEM, TG/DTA, FT-IR, and $N_2$ BET method.

• 대한기계학회논문집A
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• 제26권5호
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• pp.881-889
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• 2002

Newly developed continuous indentation technique has made nondestructive assessment of tensile properties possible. The present study was undertaken to determine new parameters for indicating time-dependent material degradation of petro-chemical plant. Continuous indentation tests were performed for Cr-Ni steel and Cr-Mo steel which are widely used as facilities of petro-chemical plant. From the results, it was found that yield strength and tensile strength cannot be used as general degradation parameters because the changes in the strengths with aging time didn't show any tendency. On the other hand, work hardening exponent and yield ratio showed consistent tendency with increasing aging time. Therefore, nam attention of this work was paid on them as new degradation parameters, and the in-field applicability of the parameters was evaluated and discussed.

• 한국가스학회지
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• 제16권6호
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• pp.123-127
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• 2012

본 연구에서는 폴리우레탄 폼의 변형이 발생하는 원인을 규명하기위해 합성된 폴리우레탄 폼을 온도와 노화시간을 다르게 하여 영구압축음율을 측정하였다. 폼의 변형의 원인을 알아보기 위해 FT-IR로 구조분석을 하였으며 TGA, DSC, DMA를 통해 열분석을 진행 하였다. 실험 결과 폼의 변형이 발생하기 위해서는 일정량 이상의 열에너지가 필요하다는 것을 알았으며 FT-IR 결과 폼의 변형이 발생으로 인한 구조의 변화가 발생하지 않는다는 것을 확인하였다. 열분석 결과 폼의 변형이 발생하는 온도 구간에서 분해에 의한 무게 감소가 없었으며 열 흐름상에는 특별한 차이가 없었다. 그러나 hard segment의 유리전이온도 이상부터 저장 모듈러스 감소율이 커졌으며 이로 인해 복원력이 감소한 것을 알았다.